POS0731 SOUTHEND GCA PROBABILITY SCORE (GCAPS) AND ULTRASOUND HALO SCORE (HS) AS MARKERS FOR DIAGNOSIS AND MONITORING OF GCA: RESULTS FROM THE PROSPECTIVE, MULTICENTER HAS-GCA STUDY
Authors: A. Sebastian, K. Van der Geest, E. Conticini, S. Inness, J. Jackson, A. Kayani, M. Khurshid, G. Klinowski, P. Macchioni, D. Prieto-Peña, C. Salvarani, M. Tariq, A. Tomelleri, B. Dasgupta
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Ultrasound (US) is recommended as the first-line imaging test in patients with suspected Giant Cell Arteritis (GCA). Traditionally, the US halo sign has been used for diagnosis. We have described a composite Halo Score that allows quantifying vascular inflammation on US. Prospective studies on response and disease monitoring are lacking. <h3>Objectives</h3> To prospectively assess the role of the US and Southend GCA pre-test probability score (GCAPS) in diagnosing and monitoring GCA patients. We report 12-month follow-up data on our current recruitment. <h3>Methods</h3> HAS GCA (IRAS#264294) is a prospective, multicentre study recruited from 7 European centres, referrals of suspected GCA to fast-track clinics. Based on the GCAPS <sup>[1]</sup>, patients were stratified in to low, intermediate and high risk categories <sup>[2]</sup>. Temporal and axillary US Halo Scores were calculated from the halo thickness and extent in bilateral temporal arteries, parietal and frontal branches (TAHS) and axillary arteries (AAHS). These scores were summed (TAHS x1 plus; AAHS x3) to generate a Total Halo Score (THS) <sup>[3]</sup>. Remission defines as the patient on prednisolone ≤ 5mg at 12 months follow up. Mann Whitney U test was used to compare baseline features between GCA and controls. Wilcoxon signed rank test was used to evaluate disease features at baseline and at 12 months in GCA patients. Sensitivity (Sn), Specificity (Sp) and ROC curve were calculated, where applicable. P value &lt;0.05 is statistically significant. <h3>Results</h3> 229 patients (84 GCA, 145 controls) have been recruited from 7 European centres: 73 completed 12-month follow-up assessments; 11 were lost to follow-up (7 died, 4 withdrew consent due to pandemic). 65 achieved remissions at 12months. Demographics, clinical features, and US results are shown (<b>Table 1</b>). Among GCA patients, 60 had cranial, 5 large-vessel and 19 mixed phenotypes. Diseases were diagnosed by US and additional tests such as PET CT. Jaw claudication (54%) and constitutional symptoms (52%) were the dominant features in GCA patients compared to controls. Median age was 75 years in GCA (60% females) and 68 years in controls (69% females). GCA and controls were stratified by GCAPS to Low risk (0% vs 46%; Sn-undefined, Sp-99), Intermediate risk (21% vs 38%; Sn-83, Sp-98) and High risk (79% vs 16%; Sn-99, Sp-91). Optimal GCAPS cut-off point was ≥12 (Sn-89, Sp-78). Median THS was 21.5 in GCA and 8 in controls. Optimal cut-off Halo Score in diagnosis was TAHS ≥6 (Sn-86, Sp-92), AAHS ≥11 (Sn-52, Sp-75), THS ≥17 (Sn-76%, Sp-91%). Baseline Halo Score and CRP levels showed positive correlation (spearman rank correlation). at 12-months follow up, median TAHS, AAHS and THS reduced from 13 to 3, 12 to 9 and 21.5 to 12, respectively (<b>Figure 1</b>). <h3>Conclusion</h3> Along with GCAPS, Halo Score successfully discriminates GCA from non GCA mimics and. HS is effective in showing 12-month response. This score may be a useful marker to monitor GCA disease activity. <h3>References</h3> [1]Laskou F et al. Clin Exp Rheumatol. 2019 [2]Sebastian A et al. RMD Open. 2020 [3]Van der Geest KSM et al. ARD 2020 <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> Alwin Sebastian: None declared, Kornelis van der Geest Speakers bureau: Roche, Grant/research support from: Abbvie, Edoardo Conticini: None declared, Sue Inness: None declared, Jo Jackson: None declared, Abdul Kayani: None declared, Muhammad Khurshid: None declared, Giulia Klinowski: None declared, Pierluigi Macchioni: None declared, Diana Prieto-Peña: None declared, Carlo Salvarani: None declared, Mohammad Tariq: None declared, Alessandro Tomelleri: None declared, Bhaskar Dasgupta Consultant of: Roche, Chugai, Sanofi, Grant/research support from: Roche, Sanofi, AbbVie, and GlaxoSmithKline.